build flake: Update conflict in blue-green pipeline job starting build prevents build from running

[smarterclayton]

https://ci.openshift.redhat.com/jenkins/job/test_pull_request_origin_extended/137/testReport/junit/(root)/Extended/_builds__Slow__openshift_pipeline_build_Blue_green_pipeline_Blue_green_pipeline_should_build_and_complete_successfully/

Generic trigger controller runs faster, this may be the root cause of this. Conflict on server should be retried in most cases.

Apr  8 18:38:42.515: INFO: Running 'oc start-build --config=/tmp/extended-test-jenkins-pipeline-1x9fj-8wn49-user.kubeconfig --namespace=extended-test-jenkins-pipeline-1x9fj-8wn49 bluegreen-pipeline -o=name'
Apr  8 18:38:42.902: INFO: Error running &{/data/src/github.com/openshift/origin/_output/local/bin/linux/amd64/oc [oc start-build --config=/tmp/extended-test-jenkins-pipeline-1x9fj-8wn49-user.kubeconfig --namespace=extended-test-jenkins-pipeline-1x9fj-8wn49 bluegreen-pipeline -o=name] []    Error from server (Conflict): Operation cannot be fulfilled on buildconfigs.build.openshift.io "bluegreen-pipeline": the object has been modified; please apply your changes to the latest version and try again
 [] <nil> 0xc421654990 exit status 1 <nil> <nil> true [0xc42002db20 0xc42002db50 0xc42002db60] [0xc42002db20 0xc42002db50 0xc42002db60] [0xc42002db28 0xc42002db48 0xc42002db58] [0x9b7d50 0x9b7e50 0x9b7e50] 0xc4212cac60 <nil>}:
StdOut>

StdErr>
Error from server (Conflict): Operation cannot be fulfilled on buildconfigs.build.openshift.io "bluegreen-pipeline": the object has been modified; please apply your changes to the latest version and try again



start-build output with args [bluegreen-pipeline -o=name]:
Error>exit status 1
StdOut>

StdErr>
Error from server (Conflict): Operation cannot be fulfilled on buildconfigs.build.openshift.io "bluegreen-pipeline": the object has been modified; please apply your changes to the latest version and try again

[AfterEach] Blue-green pipeline
  /go/src/github.com/openshift/origin/_output/local/go/src/github.com/openshift/origin/test/extended/builds/pipeline.go:271

[bparees]

assigning to @jim-minter since he has PR #13910 to address this.